Operation prohibition device for a car loading audio instrument

ABSTRACT

A car loading audio instrument adapted to be used by being connected to a car battery so that an electric power is supplied to the audio instrument and comprising a circuit breaker to break a circuit in a non-reversible manner in accordance with detection of robbery of the car loading audio instrument so that it is prohibited from being operated. A robbery is detected when two power lines supplying power are disconnected from each other.

This is a continuation of application Ser. No. 08/095,602, filed Jul.21, 1993 and now U.S. Pat. No. 5,418,761.

BACKGROUND OF THE INVENTION

This invention relates to an improvement on an operation prohibitiondevice for a car loading audio instrument serving that the audioinstrument is prohibited from being operated after it is stolen.

There has been proposed an operation prohibition device for a carloading audio instrument adapted to be unable to operate the audioinstrument after it is disconnected from a car battery when it is stolenas disclosed by U.S. Pat. No. 4,710,907, for example, which is owned bythe applicant. The U.S. Patent discloses a preset recitation code numberbeing input in order to release the prohibition of operation of theaudio instrument. Japanese Laying-open No. 60-138645 discloses that therecitation code number can be voluntarily set by an operator.

In such conventional devices, a program of a microcomputer forcontrolling an operation of the audio instrument requires to input apreset recitation code number when it is connected to an electric power.Since the audio instrument is disconnected from a car battery when it isstolen, the preset recitation code number has to be input before theaudio instrument should be operated after it is again connected to a carbattery.

Thus, it will be understood that the conventional audio instrument neverstores a condition on which it is stolen, but is adapted to beprohibited from being operated when it is connected to the car battery,which occurs when it is stolen. However, this occurs not only when it isstolen, but also when it is initially mounted on a car or when it isagain connected to the car battery after the car is checked or arranged.It will be noted-that the recitation code number is essentially requiredwhen the audio instrument is again connected to the car battery afterthe car is checked or arranged.

In case that memories such as RAM used are of inexpensive volatilememory, a backup power source is required. Nonvolatile memories are moreexpensive than volatile ones.

SUMMARY OF THE INVENTION

Accordingly, it is a principal object of the invention to provide anoperation prohibition device for a car loading audio instrument adaptedto prevent the audio instrument from being unable to be operated when itis disconnected from a car battery, which is caused by other occurencesthan robbery.

It is another object of the invention to provide an operationprohibition device for a car loading audio instrument adapted topositively prohibit the audio instrument from being operated only afterit is stolen.

In accordance with one aspect of the present invention, there isprovided an operation prohibition device for a car loading audioinstrument comprising;

at least two power supply lines extending from a car battery to said carloading audio instrument, but not through an accessory switch;

means to detect at least one of said two power supply lines beingdisconnected from said car battery;

and means to prohibit said audio instrument from being operated inaccordance with detection of said at least one of said two power supplylines being disconnected.

With either or both of the power supply lines disconnected from the carbattery when the car loading audio instrument is stolen, it isprohibited from being operated even though the accessory swicth isturned on. Thus, it will be noted that the audio instrument is neverprohibited from being operated when the audio instrument is disconnectedfrom the car battery, but not when it is stolen and that it ispositively prohibited from being operated when it is disconnected fromthe car battery by being stolen.

In accordance with another aspect of the invention, there is provided anoperation prohibition device for a car loading audio instrumentcomprising;

means to detect said car loading audio instrument being stolen;

a circuit breaker to be cut so as to break a circuit in a non-reversiblemanner in accordance with said means to detect said car loading audioinstrument being stolen;

means to detect whether said circuit breaker is cut or not;

and means to prohibit said car loading instrument from being operated inaccordance with detection of said circuit breaker being broken.

With the circuit breaker cut only when the car loading audio instrumentis stolen, the condition in which it is stolen is positively stored.Thus, it will be noted that the audio instrument is never prohibitedfrom being operated when the audio instrument is again connected to thecar battery after it is initially mounted on the car, but that it ispositively prohibited from being operated when it is connected to thecar battery after it is stolen.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the invention will beapparent from the description of the embodiment of the invention takenalong with the accompanying drawings in which;

FIG. 1 is a schematic diagram of a circuit of a car loading taperecorder constructed in accordance with one embodiment of the invention;

and FIG. 2 is a flow chart illustrating an operation of the operationprohibition device of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENT

Referring now to FIG. 1, there is shown a circuit of a car loading radioand tape recorder having an operation prohibition device constructed inaccordance with one embodiment of the invention. A car battery 1 isconnected through a dividing connector 2 and a connecting lead 14 to aterminal of a connector 3 and through a connecting lead 15 to a terminal5 of the connector 3. The dividing connector 2 is disposed at a positionsuch as an inside of a dashboard where it is never accessible. The carbattery 1 is also connected through an accessory (ACC) switch 11 to aterminal 6 of the connector 3.

A terminal 7 of the connector 3 serves to connect an antenna 12 and atape recorder 10 with each other and a terminal 8 of the connector 3serves to connect ground to the car and ground to the tape recorder 10with each other. Thus, the tape recorder 10 is connected directlythrough the terminals 4 and 5 to the car battery 1 and also through theACC switch 11 and the terminal 6 to the car battery 1.

The terminal 4 of the connector 3 is connected to one end of a coil 20disposed within the tape recorder 10 and also connected to an emitter ofa transistor 23 while the terminal 5 of the connector 3 is connected toa base of the transistor 23. Thus, it will be noted that the transistor23 is normally off because a voltage difference across the base and theemitter thereof is zero. Other end of the coil 20 is connected to oneend of a capacitor 21, the other end of which is connected to ground. Bythe coil 20 and the capacitor 21 is formed a filter which serves tointerrupt noise component from being introduced into the tape recorder10 through a power source line.

Such a power source provided through the filter is supplied through afirst power source line B1 to a tuner 63 and amplifiers which require apower source having no noise. A second power source line B2 extends froma connection point of the terminal 5 of the connector 3 and the base ofthe transistor 23 so that a power source is supplied to a mechanism 62such as an electric motor have an tendency to be hardly effected bynoise introduced into the power source line. The connection pointbetween the terminal 5 and the transistor 23 is connected through aresistor 13 to ground.

An anode of a diode 24 is connected to the other end of the coil 20while a cathode thereof is connected to one end of a capacitor 25, theother end of which is connected to ground. The cathode of the diode 24is also connected to one end of an IC protector (referred to as ICPhereinafter) 26. The ICP 26 is an overcurrent protecting element whichhas the same function as a conventional fuse.

The ICP 26 may be one commercially available as tradename ICP-F10 fromRohm Corporation, for example, which has an appearance similar to thoseof semiconductors such as normal transistors. The ICP 26 serves to breakin a non-reversible manner a circuit into which the ICP 26 is disposedin series thereto, when a current of more than predetermined value flowstherethrough. The other end of the ICP 26 is connected to a robberydetecting terminal 41 described hereinafter.

A microcomputer 40 serves to control an operation of the tape recorder10. It controls the mechanism 62 of the tape recorder 10 and the tuner63 in accordance with instructions from an operating panel 60 includingvarious operating switches.

A base of a transistor 27 is connected to a collector of the transistor23 while a collector of the transistor 27 is connected to a base of atransistor 28. A collector of the transistor 28 is connected to groundwhile an emitter of the transistor 28 is connected to the other end ofthe ICP 26. A transistor 29 has a base connected to an alarm settingterminal 42 of the microcomputer 40 described hereinafter, a collectorconnected to an emitter of the transistor 27 and an emitter connected toground. The alarm setting terminal 42 is maintained at "L" level oninitialization of the microcomputer 40.

A transistor 30 has a base connected to the other end of the ICP 26, anemitter connected to ground and a collector connected through the ACCswicth 11 and the terminal 6 of the connector 3 to a power source lineACC which supplies an electric power to the tape recorder 10. Thecollector of the transistor 30 is also connected to a base of atransistor 31, an emitter of which is connected to ground. A collectorof the transistor 31 is connected to a cathode of a light emitting diode32 disposed on a front panel of the tape recorder 10. An anode of thelight emitting diode 32 is connected to the power source line B1. Thecathode of the light emitting diode 32 is also connected to a collectorof a transistor 33, an emitter of which is connected to ground.

The alarm setting terminal 42 of the microcomputer 40 is connected to anoscillator 34 which generates pulses at a predetermined period. Anoutput of the oscillator 34 is connected to a base of the transistor 33.

The microcomputer 40 can provide a robbery prevention mode to the taperecorder 10 by means of 16 predetermined operating keys. The robberyprevention mode can be provided by turning off the ACC switch 11 afterboth of a fast forwarding (FF) key and a rewinding (REW) key on thefront panel of the tape recorder 10 are simultaneously pushed down, forexample. At that time, the alarm setting terminal 42 of themicrocomputer 40 is maintained at "H" level. The microcomputer 40detects a voltage level of the robbery detecting terminal 41 everytimethe ACC switch 11 is turned on.

An operation of the operation prohibition device of the invention willbe described with reference to a flow chart of FIG. 2 hereinafter. Inthe normal condition of FIG. 1, the tape recorder 10 has the robberyprevention mode obtained by turning off the ACC switch 11 after the FFkey and the REW key are simultaneously pushed down as illustrated inblocks 51 and 52 of FIG. 2. At that time, the alarm setting terminal 42of the microcomputer 40 is at "H" level as shown in a block 53 of FIG.2.

In the robbery prevention mode, the transistor 23 is turned off becauseof no voltage difference across the base and the emitter thereof. Thiscauses the transistors 27, 28 and 31 to be turned off and the transitors29 and 30 to be turned on. Since the alarm setting terminal 42 is at thestate of "H" level, the oscillator 34 generates pulses having apredetremined period. Thus, the transistor 33 repeats being turning onand off in synchronization with the period of the pulses from theoscillator 34 so that the light emitting diode 32 flickers. This canappeal the robbery prevention mode of the tape recorder 10 to a robberthrough a window of the car.

Such a robber as knows the tape recorder having the robbery preventionmode selected cannot be used even though he steals it will lose a desireto steal it. Thus, it will be noted that the tape recorder can bepositively prevented from being stolen.

A case in which the tape recorder 10 is stolen even though the lightemitting diode 32 flickers will be described herein just below. Therobber will invade the car by a suitable method. Thereafter, he willremove the tape recorder 10 from the car by unfastening screws and nutswhich fasten the tape recorder 10 on the car and then remove theconnector 3 which connects the tape recorder 10 to the car or cut theconnecting leads 14 and 15.

In case that the connector 3 is removed, the base and the emitter of thetransistor 23 are broken from each other because of the connector 3being removed. Thus, the base of the transistor 23 is at ground levelthrough a resistor 13, which causes the transistor 23 to be turned on.Since the transistror 29 is already at the on-state, the transistor 27is also turned on.

By turning on the transistors 27 and 29 is turned on the transistor 28,which causes the other end of the ICP 26 to be rapidly at ground level.Thus, an overcurrent discharges from the capacitors 21 and 25 throughthe ICP 26. This causes the ICP 26 to be cut so that the circuit intowhich the ICP 26 is disposed is broken. It should be noted that theovercurrent from the capacitors 21 and 25 flows through the ICP 26 onlyfor a discharging time, but that the ICP 26 can be broken only forapproximately 0.1 second. Thus, it will be noted that the capacitors 21and 25 may be of such capacitance as can hold such a breaking time.

In case that the robber cuts the connecting lead 15 extending betweenthe connector 2 and the terminal 5 of the connector 3, the base of thetransistor 23 is at ground level through the resistor 13 because of noconnection between the base of the transistor 23 and the car battery 1.This causes the transistor 23 to be turned on and also the transistor 27to be turned on because of the transistor 29 being turned on.

By turning on the transistors 27 and 29 is turned on the transistor 28,which causes the other end of the ICP 26 to be rapidly at ground level.Thus, an overcurrent from the car battery through the connecting lead 14remaining connected flows through the coil 20 and the diode 24 and thenthrough the ICP 26. Thus, the ICP 26 is immdeiately broken.

In case that the robber cuts the connecting lead 14 extending betweenthe connector 2 and the terminal 4 of the connector 3, the capacitor 21holds a voltage applied across both ends thereof for a while even afterthe connecting lead 14 is cut. Thereafter, as the connecting lead 15extending between the connector 2 and the terminal 5 of the connector 3is cut, the transistor 23 is turned on because of the base thereof beingat ground level through the resistor 13. Thus, a current flowing fromthe capacitor 21 through the coil 20 and the transistor 23 turns on thetranistor 27.

The transistor 28 is turned on by the turned-on transistor 27. Since thealarm setting terminal 42 is at "H" level, the transistor 29 is turnedon. Thus, a current from the capacitor 21 flows through the diode 24,the ICP 26 and the transistor 28 to ground. The discharged currentbreaks the ICP 26 so that the circuit is cut.

After the capacitor 21 is disconnected from the car battery 1 by cuttingthe connecting lead 14, a small amount of current tends to flow from thecapacitor 21 through the power source line B1 to the amplifiers and thetuner 63 so that a voltage across both ends of the capacitor 21 isgradually lowered. Thus, it will be considered that a breaking currentcannot flow through the ICP 26 because of the voltage across theterminals of the capacitor 21 being lowered, which will fearfully occurwhen it takes substantial time that the connecting lead 15 is cut afterthe connecting lead 14 is cut.

However, since the capacitor 25 is connected in parallel to thecapacitor 21 and also since the diode 24 is disposed between the the ICP26 and the capacitor 21 so that the capacitor 25 is never dischargedthrough the power source line B1, the capacitor 25 has voltage droplower than the capacitor 21 has. Thus, it will be noted that thebreaking current can positively flow through the ICP 26 by a cooperationof the capacitors 21 and 25 when the connecting lead 15 is cut.

It will be considered that the terminal voltages of the capacitors 21and 25 are lowered so that a predetermined amount of breaking currentcannot flow through the ICP 26. This will occur when it takessubstantially long time that the connecting lead 15 is cut after theconnecting lead 14 is cut. However, since the robber tends to steal thetape recorder 10 as soon as possible, the voltage drop of the capacitors21 and 25 during 16 such a long time will be negligible.

In this manner, as the connector 3 is removed or the connecting leads 14and 15 are cut when the tape recorder 10 is stolen, the ICP 26 isbroken. Therefore, even though the stolen tape recorder 10 is mounted ona car and the ACC switch 11 is turned on as shown in a block 55 in FIG.2, the tape recorder 10 cannot be operated. That is because themicrocomputer 40 controls the alarm setting terminal 42 to be at "L"level as shown in a block 56 in FIG. 2 and then detects the level of therobbery detection-terminal 41 as shown in a block 57 in FIG. 2, but therobbery detection terminal 41 is maintained at "L" level because of theICP 26 being broken. Thus, the microcomputer 40 is never operated by allthe keys on the panel of the tape recorder 10, which prohibits the taperecorder 10 from being operated as shown in a block 58 in FIG. 2.

Since the ICP 26 is broken when the ACC switch 11 is turned on, thetransistor 30 is turned off. This causes the transistor 31 to be turnedon and therefore the cathode of the light emitting diode 32 to be atground level. Thus, the light emitting diode 32 continues to be lighted,which indicates that the tape recorder 10 is in the condition of beingprohibited from being operated.

If the robber can replace the broken ICP 26 by a new ICP, the taperecorder 10 will be able to be operated. Even though the robber has aknowledge of electricity, since the tape recroder 10 normally has manyICPs for protection of the circuits and complicated appearances, he willbe unable to determine whether the ICP 26 is broken or not. Also, sincethe ICP 26 has an appearance similar to those of semiconductors such astransistors, the ICP 26 will be practically unable to be replaced unlesshe knows the detailed construction of the circuits.

In the condition that the robbery protection mode is not set because theFF key and the REW key are not simultaneously pushed down as shownin-the block 51 in FIG. 2, even though the ACC switch 11 is turned offas shown in a block 54 in FIG. 2, the alarm setting terminal 42 ismaintained at "L" level. Thus, the oscillator 34 generates no pulses,which causes the light emitting diode 32 to be maintained at the stateof being turned off.

In this condition, as the robber removes the connector 3, thetransistors 23, 27 and 28 are turned off because of the transistor 29being off. Thus, no overcurrent flows through the ICP 26, which causesthe ICP 26 to be never broken. Since the robbery protection mode is notset, the tape recorder 10 can be normally operated when the taperecorder 10 is connected to a car battery after it is stolen. In thecondition that the robbery protection mode is not set, even though theACC switch 11 is turned off and the connector 3 is removed when the taperecorder 10 is removed for being repaired, the ICP 26 is never broken.Thus, it will be noted that when the repaired tape recorder 10 is againmounted on the car and connected to the car battery 1, it can benormally operated.

After the FF key and the REW key are simultaneously pushed down as shownin the block 51 in FIG. 2, 5 seconds lapse without turning off the ACCswitch 11 as shown in the block 52 and a block 59 in FIG. 2, whichregards no simultaneous operation of the FF key and the REW key to bemade. Thus, even though the the ACC switch 11 is turned off, the alarmsetting terminal 42 is maintained at "L" level as shown in the blocks54, 55 and 56 in FIG. 2.

When the car battery is to be replaced, the connecting leads are removedfrom the terminals of the car battery. In this case, since the base andthe emitter of the transistor 23 are connected to each other through theconnector 2 and the voltage across the capacitor 21 is applied to thebase and the emitter of the transistor 23, the transistor 23 is neverturned on and as a result the ICP 26 is never broken.

Although a single embodiment of the invention has been described andillustrated with reference to the accompanying drawings, it will beunderstood by those skilled in the art that it is by way of example, andthat various changes and modifications may be made without departingfrom the spirit and scope of the invention.

For example, although, in the aforementioned embodiment, after it isdetected that the two power supply lines are cut, the IC protector isbroken by the overcurrent flowing therethrough so that the audioinstrument is prohibited from being operated, it may be unable to beoperated unless the recitation code number is input.

Furthermore, although, in the aforementioned embodiment, two powersupply lines are connected to the single connector, they may beconnected to respective connectors.

Although, in the aforementioned embodiment, an IC protector is used asmeans to detect and store that the audio instrument is stolen, there maybe used a conventional glass tube type fuse, which may be preferably ofsuch a type as is broken with a small amount of current and/or as berapidly broken. However, in case that such a glass tube type fuse isused, the condition of the fuse being broken can be visiblyacknowledged. Thus, the robber can disadvantageously replace the brokenfuse by a new one so that the tape recorder can be operated.

That is why the IC protector is preferably used because whether it isbroken or not cannot be visibly aknowledged and it cannot be replacedunless the robber has the knowledge of electricity as aforementioned.

Actuators for switches may be provided in a case of the tape recorder sothat the switches have states changed when the audio instrument isremoved from the car and the circuit breaker is broken in accordancewith the change of states of the switches.

Thus, it should be understood that this invention is defined only to theappended claims.

What is claimed is:
 1. An operation prohibition device for a car loadingaudio instrument comprising;at least two power supply lines connectedtogether and extending from a car battery to said car loading audioinstrument, but not through an accessory switch; means to detect saidtwo power supply lines being disconnected from each other; and means toprohibit said car loading audio instrument from being operated when saidmeans to detect said two power supply lines being disconnected detectssaid two power supply lines being disconnected from each other toprovide a prohibition instruction to said instrument.
 2. An operationprohibition device for a car loading audio instrument as set forth inclaim 1, and said means to detect said two power supply lines beingdisconnected from each other comprises a circuit breaker.
 3. Anoperation prohibition device for a car loading audio instrument as setforth in claim 2, and said circuit breaker comprises an IC protector. 4.An operation prohibition device for a car loading audio instrument asset forth in claim 2, and said means to detect said two power supplylines being disconnected from each other comprises at least onecapacitor charged through one of said two power supply lines and meansto detect a voltage difference between said two power supply lines. 5.An operation prohibition device for a car loading audio instrument asset forth in claim 4, and said means to detect said two power supplylines being disconnected from each other further comprises asemiconductor switch which is turned on when said two power supply linesare disconnected from each other and through which overcurrent throughsaid circuit breaker flows from said at least one capacitor.
 6. Anoperation prohibition device for a car loading audio instrument as setforth in claim 1, and said means to detect said two power supply linesbeing disconnected from each other comprises a plurality of capacitorscharged through one of said two power supply lines, means to interrupt adownstream one of said adjacent capacitors from being discharged andmeans to detect a voltage difference between said two power supplylines.
 7. An operation prohibition device for a car loading audioinstrument as set forth in claim 6, and said means to detect said twopower supply lines being disconnected from each other further comprisesa semiconductor switch which is turned on when said two power supplylines are disconnected from each other and through which overcurrentthrough said circuit breaker flows from said capacitors.
 8. An operationprohibition device for a car loading audio instrument as set forth inclaim 1, and said two power supply lines are connected to each otherthrough a connector for connecting said car loading audio instrumentwith said car whereby said means to detect said two power supply linesbeing disconnected from each other is operated when said connector isdisconnected.
 9. An operation prohibition device for a car loading audioinstrument as set forth in claim 1, and further comprising means to seta robbery prevention mode in which said means to detect said two powersupply lines being disconnected from each other is operated.